Gas burner for a cooktop

ABSTRACT

A gas burner comprises a flame ring, a Venturi tube to feed said flame ring, and a gas injector having a nozzle with an orifice to inject a burnable gas in said Venturi tube to feed said flame ring, wherein a flow perturbation element is provided in a region between said orifice and a middle portion of said Venturi tube to impact the air-gas mixing.

The present invention relates to an improved gas burner for a cooktop.

A gas burner for a cooktop generally comprises at least a burningportion having a flame ring, and a gas injector to feed the flame ringwith an ignitable gas medium. In particular, the burning portioncomprises a Venturi tube having an inlet facing the gas injector and anoutlet connected to the flame ring. The Venturi tube is placed below theflame ring and is substantially perpendicular with respect to the ringitself. The Venturi tube is designed to generate a mixing of air and gasfor a more efficient and stable burning flame at the flame ring when thegas burner is functioning.

In particular, the inlet of the Venturi tube may be spaced from the gasinjector and has a cross section that is large enough that both air andgas can enter the Venturi tube. When burnable gas is injected in theVenturi tube, air is dragged by the gas flow and the mixing takes placewithin the path from the inlet of the Venturi tube to the flame ring.

When a gas burner is connected to a supply of ignitable gas having a lowpressure, e.g. a household gas supply, an optimal mixing of gas and airrequires a quite long Venturi tube.

In some cases, it is not possible to provide a long Venturi tube toprovide optimal air/gas mixing because a shortened burning portion and aflattened cooktop configuration are preferred, in particular on the massmarket. In such a case it is preferred to provide more room for otherkitchen appliances below the cooktop. Furthermore, more kitchen designoptions are available for the user. In particular, a flattened gascooktop may be placed more easily within a kitchen, in particular withina small kitchen.

It is known to reduce the length of a Venturi tube within a gas burnerfor a cooktop. However, when the Venturi tube is shortened, mixing ofair and gas is not optimal. In such a case, some regions of the flamering are fed by an air/gas mixture that is rich in gas and other regionsof the flame ring are fed by an air/gas mixture that is rich in air.This condition has several disadvantages that are mitigated by the airpresent in a region above the cooktop and surrounding the flame ring. Inorder to obtain a stable flame and a low unburned gas level when air/gasmixing is poor, the cooking plane for a cooking appliance shall beplaced relatively far from the flame ring so that air surrounding theflame ring is such to improve the stability of the flame and the burningconditions. However, when the cooking plane is far from the flame ringthe efficiency of heat transfer from the burner to the cooking appliancedecreases.

A purpose of the present invention is to provide a gas burner for acooktop with an increased mixing capability.

In compliance with the above aims, according to the present inventionthere is provided a gas burner comprising a flame ring, a Venturi tubeto feed said flame ring with air/gas mix, and a gas injector having anozzle with an orifice to inject a burnable gas into said Venturi tube,wherein a flow perturbation element is provided in a region between saidorifice and a middle portion of said Venturi tube to impact the air-gasmixing.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said flow perturbation element is set outside ofsaid Venturi tube and between said inlet and said orifice.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said flow perturbation element is carried by saidnozzle.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said flow perturbation element comprises a passiveprojection.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said projection comprises a planar wall.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said nozzle is a single body with said projection.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said flow perturbation element is distanced froman axis of said orifice.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that the position of said projection is given by:

0.5*D<X<5*D

0.5*D<Y<4*D

Where:

D is the diameter of said orifice;

X is the height of a top edge of said projection with respect to saidorifice;

Y is the distance of said projection from said axis.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said flow perturbation element comprises a furtherprojection.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that the position of said further projection is givenby:

0.5*D<X2<5*D

0.5*D<Y2<4*D

Where:

D is the diameter of said orifice;

X2 is the height of a further top edge of said further projection withrespect to said orifice;

Y2 is the distance of said further projection from said axis.

Preferably, though not necessarily, the gas burner is furthermore,characterized in that said projection and said further projection are onopposite sides with respect to said axis.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said further projection is different from saidprojection.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said projection and said further projection definea slot.

Preferably, though not necessarily, the gas burner is furthermorecharacterized in that said Venturi tube comprises a diffuser having adivergent cross section along the gas flow to feed said flame ring andin that said flow perturbation element is placed upstream of saiddivergent portion.

In compliance with the above aims, according to the present inventionthere is further provided a method of operating a gas burner comprisinga flame ring, a Venturi tube to feed said flame ring with an air/gasmixture and a gas injector having a nozzle with an orifice to inject aburnable gas in said Venturi tube, by providing a flow perturbationelement in a region between said orifice and a middle portion of saidVenturi tube to impact the air-gas mixing.

Preferably, though not necessarily, the method is further characterizedin that said flow perturbation element is carried by said nozzle andthat said nozzle is releasably connectable to a body of said injector.

A non-limiting embodiment of the present invention will now bedescribed, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 is a perspective view of a gas burner according to the presentinvention;

FIG. 2 is a longitudinal cross section of FIG. 1;

FIG. 3 a provides a perspective view and a correspondent longitudinalcross section of a nozzle for a gas burner according to prior art; and

FIGS. 3 b to e provide several embodiments, each of which is illustratedboth in perspective view and corresponding longitudinal cross section,of a gas nozzle for a gas burner according to the present invention.

With reference to FIG. 1, reference number 1 indicates as a whole a gasburner for a cooktop having a flame ring 2 to generate one or more ringsof flames and a Venturi tube 3 supplying flame ring 2 with an air/gasmixture. Gas burner 1 further comprises a gas injector 4 having a nozzle5 facing an inlet 6 of Venturi tube 3 to feed gas into the Venturi tube3. Optionally, gas burner 1 comprises a burner body 1 a extendingradially from Venturi tube 3 and supporting flame ring 2. Burner body 1a can be supported by Venturi tube 3, as shown in FIG. 2.

Preferably, gas burner 1 comprises also a support member 7 defining aresting surface for positioning flame ring 2. In the illustratedembodiment, support member 7 also defines a rigid connection between theabove-mentioned resting surface and the gas injector 4 and it is soshaped and dimensioned as to set a proper distance between nozzle 5 andinlet 6 of the Venturi tube. According to the embodiment of FIG. 2, theresting surface contacts a flange 3 a of the Venturi tube 3 so thatflame ring 2 is positioned in space, in particular along the verticaldirection, by burner body 1 a and its shape. In a preferred embodiment,support member 7 and a main body 8 of gas injector 4 are a single body.In the particular embodiment here illustrated, the main body 8 of gasinjector 4 is an L-shaped body, which has an inlet portion directedhorizontally and releasably connected to a burnable gas line (notshown), e.g. a household gas line, and an outlet portion directedvertically and upwards. Nozzle 5 is connected, preferably releasablyconnected, to the outlet portion of the main body 8. Nevertheless, otherconfigurations can be provided to hold flame ring 2 and Venturi tube 3in a suitable relative position with respect to nozzle 5. In particular,various connections of the flame ring 2 with Venturi tube 3 and ahorizontal main plate (not shown) of the cooktop are possible. In oneconfiguration, Venturi tube 3 is releasably connected, e.g. by screwing,to the main plate of the cooktop and flame ring 2 is resting on top ofVenturi tube 3 by gravity.

FIG. 3 a illustrate in greater detail nozzle 5 according to the priorart. Such nozzle has a flat head surface 9 and an orifice 10 to injectgas beyond head surface 9.

In a gas burner according to the prior art, air/gas mixing in the areaimmediately downstream nozzle 5 is insufficient, in particular whenburnable gas is provided through gas injector 4 at a low pressure, i.e.the pressure in a household or restaurant supply line or, more ingeneral, in a city or municipal gas system. By contrast, a high pressuregas feed can be provided when a pressurized gas cylinder is connected toa gas burner, e.g. in camping gas cookers.

According to the present invention a flow perturbing element is providedeither outside or inside an initial portion of Venturi tube 3 downstreamof orifice 10. Depending on the many possible configurations, a Venturitube 3 for a gas burner fed by ignitable gas having a low pressurizationgenerally comprises two longitudinal portions: a lower portion 15defining inlet 6 and an upper portion, or diffuser, 16 between the lowerportion 15 and flame ring 2. The lower portion 15 and the upper portions16 join at a middle portion 17 of the Venturi tube 3. Diffuser 16 has adivergent cross section towards flame ring 2 along the air/gas mixtureflow and has the function of increasing the mixing of air and gasupstream of flame ring 2. The Applicant has found that when a flowperturbing element is provided downstream of orifice 10 and upstream ofdiffuser 16, i.e. between the orifice 10 and the middle portion 17,air/gas mixing is improved. Diffuser 16 can be used when vertical spaceavailable for gas burner 1 is reduced and gas is provided at a lowpressure, in order to improve mixing.

FIG. 3 b discloses a nozzle 20 for a gas burner according to a firstembodiment of the present invention, to be used in gas burner 1 in placeof nozzle 5. Nozzle 20 is releasably connected to main body 8.

Nozzle 20 has a shaped head portion 21 defining a projection 22 whoseprofile intersects the trajectory of gas exiting orifice 10. If comparedwith the head portion of nozzle 5 of FIG. 3 a, the head portion 21 hassubstantially the same height at projection 22 and a much lower heightin the remaining portion. Moreover, the head portion 21 is (seen fromthe above) preferably hexagonal, but may have any other shape thatallows easy coupling of the nozzle 20 onto the main body 8. Nozzle 20further comprises a connecting portion 25 set below head portion 21, forconnecting nozzle 20 to main body 8. Head portion 21 and connectingportion 25 preferably form a single body. Connecting portion 25 ispreferably cylindrical and externally threaded, so that it can becoupled with an internally threaded portion of the exiting hole of themain body 8. Head portion 21 normally projects from main body 8 and isplaced below Venturi tube 3 to face inlet 6.

Advantageously, the circle circumscribing the head portion 21 has agreater diameter than the connecting portion 25, and the nozzle 20comprises also a middle frusto-conical portion 26 joining the headportion 21 with the connecting portion 25, designed to abut on the edgeof the exiting hole of gas injector 4.

The gas passage inside the nozzle 20 includes, in addition to theexiting orifice 10, an entrance hole 27, which is slightly smaller thanthe exiting hole of the main body 8 but larger than the orifice 10, anda middle tapered section 28 connecting the entrance hole 27 to theorifice 10.

When the gas burner according to the invention is functioning, the gasexiting from nozzle 20 tends to expand according to a tapered trajectorydiverging from orifice 10. The projection 22 of head portion 21 isshaped and located to interfere with the gas flow exiting orifice 10according to said tapered trajectory. This causes a perturbation of thegas flow that increases air/gas mixing. Furthermore, projection 22 ofnozzle 20 perturbs the gas flow in a passive way, i.e. projection is notenergized or actuated and perturbation is obtained because theprojection functions as an obstacle to the gas flow. In this way flowperturbation is easily and cost effectively obtained.

According to the embodiment of FIG. 3 b, shaped head portion 21 isasymmetric with respect to an axis A of orifice 10. Preferably, shapedhead portion 21 comprises a single projection 22 having a lateral wall23 distanced from and facing axis A. Projection 22 extends from a planecontaining an edge 10′ of orifice 10. Edge 10′ may be circular.

Position and shape of lateral wall 23 is such to reach a good compromisebetween two conflicting issues. On one side the closer the wall 23 toaxis A the higher the turbulence generated. On the other side, thefarther the wall 23 from axis A the higher the gas flow speed. In caseof an excessive turbulence generated at the inlet 6 of Venturi tube 3,gas flow is slow and combustion is negatively impacted.

According to a preferred embodiment, let X and Y be defined as theheight and horizontal distance of an upper edge 24 of lateral wall 23from axis A respectively; and D be the diameter of orifice 10. A goodcompromise on the above conflicting issues is obtained when the aboveparameters meet conditions 1.1 and 1.2 below.

Lateral wall 23 may either be planar, as illustrated in FIG. 3 b inorder to be easily manufactured, or be shaped differently within therange defined by the conditions below.

FIG. 3 c refers to a nozzle 30 according to a second embodiment of thepresent invention. Numerals identical to those of nozzle 20 are used inconnection with nozzle 30 to designate elements that are functionallyidentical to those of nozzle 20. In practice, the only differences arein the upper part of the head portion.

Nozzle 30 comprises a shaped head portion 31 that is symmetrical withrespect to axis A of orifice 10. In particular head portion 31 comprisesa projection similar—but functionally identical, and therefore indicatedwith the same number—to projection 22 of FIG. 3 b, and a furtherprojection 32 that is opposite to projection 22 with respect to axis A.The further projection 32 increases the turbulence of the gas flow.Projections 22 and 32 define a straight slot 34 as shown in FIG. 3 c.The slot 33, in particular, defines an easy-to-manufacture embodiment toobtain the desired increase of air/gas mixing.

According to a preferred embodiment, let X be defined as the height ofprojections 22 and 32; Y be the distance between (upper) edge 24 and acorresponding (upper) edge 33 of projection 32; and D be the diameter oforifice 10. A good compromise on the above conflicting issues isobtained when the above parameters meet conditions 1.1 and 1.2.

The lateral wall facing axis A of each projection 22, 32 may either beplanar, as illustrated in FIG. 3 c, or be shaped differently within therange defined by the conditions below. Moreover, such lateral walls maybe vertical, as illustrated in FIG. 3 c, or inclined, as the lateralwall of projection 22 in FIG. 3 b.

FIG. 3 d refers to a nozzle 40 according to a third embodiment of thepresent invention. Numerals identical to those of nozzle 30 are used inconnection with nozzle 40 to designate elements that are functionallyidentical to those of nozzles 20 or 30.

Nozzle 40 comprises a shaped head portion 41 that is asymmetrical withrespect to axis A of orifice 10. In particular head portion 41 comprisesa projection similar—but functionally identical, and therefore indicatedwith the same number - to projection 22 of FIGS. 3 b and 3 c, and afurther projection 42 that is opposite to projection 22 with respect toaxis A, wherein projection 22 is shorter and closer to axis A thanprojection 42.

According to a preferred embodiment, let X1 and X2 be defined as theheight of projections 22 and 42 respectively; Y1 and Y2 be the distancebetween axis A and (upper) edge 24 and between axis A and acorresponding (upper) edge 43 of projection 42 respectively; and D bethe diameter of orifice 10. A good compromise on the above conflictingissues is obtained when the above parameters meet conditions 1.1 and 1.2below.

The lateral wall facing axis A of each projection 22, 42 may either beplanar, as illustrated in FIG. 3 d, or be shaped differently within therange defined by the conditions below. Moreover, such lateral walls maybe vertical, as illustrated in FIG. 3 d, or inclined, as the lateralwall of projection 22 in FIG. 3 b.

FIG. 3 e refers to a nozzle 50 according to a fourth embodiment of thepresent invention. Numerals identical to those of nozzle 40 are used inconnection with nozzle 50 to designate elements that are functionallyidentical to those of nozzles 20 or 30 or 40.

Nozzle 50 comprises a flat head portion 51 similar to that of FIG. 3 a,but combined with a flow perturbing element 52 having a curved lateralwall 53 positioned in proximity of orifice 10. Perturbing element 52 maybe a cylinder, in particular a circular and straight cylinder that issubstantially perpendicular to axis A. Perturbing element 52 may beseparated from flat head surface 9 as shown in the cross section of FIG.3 e.

According to a preferred embodiment, let X be defined as the height ofan upper edge 54 of lateral wall 23; Y be the distance betweenperturbing element 52—in particular its lateral edge 53—and axis A; andD be the diameter of orifice 10. A good performance of the gas burner isobtained when the above parameters meet the following conditions:

0.5*D<X, X1, X2<5*D  (1.1)

0.5*D<Y, Y1, Y2<4*D  (1.2)

The lateral wall facing axis A of perturbing element 52 may either becurved, as illustrated in FIG. 3 e, or be shaped as a prism within therange defined by the above relationships.

When the position of the flow perturbing element satisfies conditions1.1 and 1.2, the percentage of unburned gas considerably decreases, allother conditions remaining equal with respect to a gas burner that isnot provided with a flow perturbing element.

According to the present invention, prior art nozzle 5 can besubstituted in a very easy way by any of nozzles 20, 30, 40 or 50. It istherefore possible to upgrade an existing gas burner in order to obtainan improved air/gas mix. This is particularly easy when nozzle 5 isreleasably attached to main body 8 of injector 4.

Clearly, changes may be made to the gas burner 1 as described abovewithout, however, departing from the scope of the present invention.

For example the Venturi tube 3 may have further configurations and, inparticular, diffuser element 16 can be substituted by a constant crosssection tubular element or by a portion that is convergent towards theflame ring along the gas flow direction. In particular, a constant crosssection tubular element is used when a wide vertical space is available,as for example in oven gas burners. In such a case, middle portion islocated substantially half way of the Venturi tube 3. However, this isnot the case when Venturi tube 3 comprises diffuser 16. In such aninstance middle portion 17 is upstream of diffuser 16.

Burner body 1 a, flame ring 2 and Venturi tube 3 can be connected indifferent ways, either by a combination of resting surfaces that areloaded by gravity force and are designed for a manual disassembly, or byrigid connections. In particular it is even possible that burner body 1a, flame ring 2 and Venturi tube 3 be manufactured as a single body bycasting.

1. Gas burner (1) comprising a flame ring (2), a Venturi tube (3) tofeed said flame ring (2) with air/gas mixture and a gas injector (4)having a nozzle (20, 30, 40, 50) with an orifice (10) to inject aburnable gas in said Venturi tube (3), characterized in that a flowperturbation element (22, 32, 42, 52) is provided in a region betweensaid orifice (10) and a middle portion (17) of said Venturi tube (3) toimpact the air-gas mixing.
 2. Gas burner according to claim 1,characterized in that said flow perturbation element (22, 32, 42, 52) isset outside of said Venturi tube (3) and between an inlet (6) of saidVenturi tube and said orifice (10).
 3. Gas burner according to claim 2,characterized in that said flow perturbation element (22, 32, 42) iscarried by said nozzle (20, 30, 40, 50).
 4. Gas burner according toclaim 1, characterized in that said flow perturbation element (22, 32,42, 52) comprises at least an upward projection of said nozzle extendingbeyond the exit of the orifice (10) in a vertical direction.
 5. Gasburner according to claim 4, characterized in that said flowperturbation element (22, 32, 42) comprises a planar wall (23) facing acentral axis (A) of said orifice (10).
 6. Gas burner according to claim5, characterized in that said nozzle (20, 30, 40, 50) is a single bodywith said projection (22, 32, 42).
 7. Gas burner according to claim 1,characterized in that said flow perturbation element (22, 32, 42, 52) isdistanced from a central axis (A) of said orifice (10).
 8. Gas burneraccording to claim 4 characterized in that the position of saidperturbation element (22, 52) is given by:0.5*D<X<5*D0.5*D<Y<4*D Where: D is the diameter of said orifice (10); X is theheight of a top edge (24, 54) of said perturbation element (22 ,52) withrespect to the exit of said orifice (10); Y is the distance of saidperturbation element (22, 52) from said axis (A).
 9. Gas burneraccording to claim 1, characterized in that said flow perturbationelement comprises a further perturbation element (32, 42).
 10. Gasburner according to claim 9, characterized in that the position of saidfurther perturbation element (32, 42) is given by:0.5*D<X2<5*D0.5*D<Y2<4*D Where: X2 is the height of a further top edge (33, 43) ofsaid further perturbation element (32, 42) with respect to said orifice(10); Y2 is the distance of said further perturbation element (32, 42)from said axis (A).
 11. Gas burner according to claim 9, characterizedin that said perturbation element (22) and said further perturbationelement (32, 42) are on opposite sides with respect to said axis (A).12. Gas burner according to claim 9 characterized in that saidperturbation element (22) and said further perturbation element (32, 42)define a slot therebetween.
 13. Gas burner according to claim 1,characterized in that said Venturi tube (3) comprises a diffuser (16)having a divergent cross section along the gas flow direction to feedsaid flame ring (2) and in that said flow perturbation element (22, 32,42, 52) is placed upstream of said divergent portion (16).
 14. Method ofoperating a gas burner (1) comprising a flame ring (2), a Venturi tube(3) to feed said flame ring (2) with air/gas mixture and a gas injector(4) having a nozzle (20, 30, 40, 50) with an orifice (10) to inject aburnable gas in said Venturi tube (3), by providing a flow perturbationelement (22, 32, 42, 52) in a region between said orifice (10) and amiddle portion (17) of said Venturi tube (3) to impact the air-gasmixing.
 15. Method according to claim 14, characterized in that saidflow perturbation element (22, 32, 42) is carried by said nozzle (10)and that said nozzle is releasably connectable to a body (8) of saidinjector (4).